JP2022518480A - A positive electrode active material containing a lithium nickel-based oxide doped with a doping element, and a secondary battery containing the same. - Google Patents

Abstract

The present invention contains a lithium nickel-based oxide doped with a doping element (M'), wherein the doping element (M') is one or more selected from the group consisting of titanium (Ti) and magnesium (Mg). When the doping element (M') is Ti, the doping content is 3000 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element, and the doping element (M') is Mg. At this time, the doping content is 500 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element, and when the doping element (M') is Ti and Mg, the total doping content is doping. Provided is a positive electrode active material for a secondary battery, which is 3500 ppm to 5000 ppm based on the total amount of lithium nickel-based oxide excluding elements.

Description

Mutual reference with related applications This application has priority based on Korean Patent Application No. 10-2019-0154435 dated November 27, 2019 and Korean Patent Application No. 10-2020-0118542 dated September 15, 2020. All content claimed in the interest and disclosed in the literature of the Korean patent application is included as part of this specification.

The present invention relates to a positive electrode active material containing a lithium nickel-based oxide doped with a doping element, and a secondary battery containing the same.

Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative energy and clean energy is increasing, and as part of this, the fields most actively studied are the fields of power generation and electricity storage using electrochemicals.

At present, a secondary battery is mentioned as a typical example of an electrochemical element using such electrochemical energy, and its range of use is expanding more and more.

Recently, with the increase in technological development and demand for portable devices such as portable computers, portable phones, and cameras, the demand for secondary batteries as an energy source has increased sharply, and such secondary batteries have increased rapidly. Of these, much research has been conducted on lithium secondary batteries that exhibit high energy density and operating potential, have a long cycle life, and have a low self-discharge rate, and have been commercialized and widely used.

In addition, as interest in environmental issues grows, much research is being carried out on electric vehicles, hybrid electric vehicles, etc. that can replace vehicles that use fossil fuels, such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution. ing. Nickel-metal hydride secondary batteries are mainly used as the power source for such electric vehicles and hybrid electric vehicles, but research using lithium secondary batteries with high energy density and discharge voltage is being actively promoted. It is in the stage of commercialization.

Currently, as the positive electrode material of the lithium secondary battery, LiCoO ₂ , a three-component system (NMC / NCA), LiMnO ₄ , LiFePO ₄ , and the like are used. Of these, LiCoO ₂ has the problem that the price of cobalt is high and the capacity is small at the same voltage as compared to the three-component system, and in order to increase the capacity of the secondary battery, the three components have a high Ni content. The amount of system used is gradually increasing.

On the other hand, when a positive electrode is manufactured using such a positive electrode material, a process of rolling the electrode is performed during the electrode process. At this time, the rolling density is increased in order to increase the electrode density of the positive electrode.

However, when the rolling pressure is increased in order to increase the rolling density in this way, cracks in the particles appear, and in this case, the side reaction between the active material and the electrolytic solution is accelerated as the specific surface area of the active material increases. Therefore, there is a problem that a large amount of gas is generated and the life characteristic is sharply deteriorated.

Therefore, the current situation is that there is an urgent need to develop a technology that can solve the above-mentioned problems, prevent the particles from cracking even at a high rolling pressure, and solve the above-mentioned problems.

The present invention solves the above problems, minimizes cracking of the positive electrode active material even during rolling at high pressure, and prevents side reactions of the electrolytic solution due to an increase in the specific surface area of the positive electrode active material to generate gas. To provide a positive electrode active material capable of improving life characteristics while solving the problem of increased resistance during high temperature storage, and a secondary battery containing the same.

Terms and words used herein and in the scope of claims shall not be construed in a normal or lexical sense and the inventor shall use the terms to best describe his invention. It must be interpreted with meanings and concepts that are consistent with the technical ideas of the invention, in accordance with the principle that concepts can be properly defined.

Hereinafter, the positive electrode active material according to the embodiment of the present invention and the secondary battery containing the positive electrode active material will be described.

According to one embodiment of the invention, it comprises a lithium nickel-based oxide doped with a doping element (M').
The doping element (M') is one or more selected from the group consisting of titanium (Ti) and magnesium (Mg).
When the doping element (M') is Ti, the doping content is 3000 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element.
When the doping element (M') is Mg, the doping content is 500 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element.
When the doping element (M') is Ti and Mg, the positive electrode active material for a secondary battery has a total doping content of 3500 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element. To.

Specifically, when the doping element (M') is Ti, the doping content of Ti may be in the above range based on the total amount of the lithium nickel-based oxide excluding the doping element, and more specifically, 3000 ppm. It may be up to 4000 ppm.

Alternatively, when the doping element (M') is Mg, the doping content of Mg may be in the above range based on the total amount of the lithium nickel-based oxide excluding the doping element, and more specifically, 2000 ppm to 4000 ppm. It may be.

Alternatively, when the doping element (M') is Ti and Mg, the total doping content may be in the above range based on the total amount of the lithium nickel-based oxide excluding the doping element, and more specifically, 4000 ppm or more. It may be 5000 ppm. The doping content ratio of Ti and Mg may be 1: 9 to 9: 1, specifically 5: 5 to 9: 1, based on the weight.

The doped lithium nickel-based oxide may be a positive electrode active material for a secondary battery represented by the following chemical formula 1.
Li _a Ni _{1-x-y-z Co x My} M'z O _2-w A _w (1)
In the above formula,
M is at least one selected from the group consisting of Mn and Al.
M'is at least one selected from the group consisting of Ti and Mg.
A is an oxygen-substituted halogen and
1.00 ≦ a ≦ 1.5, 0 <x <y, 0.2 ≦ x + y ≦ 0.4, and 0 ≦ w ≦ 0.001, and z is defined in claim 1 by a doping element. It is determined according to the content of the product.

Specifically, M may be a positive electrode active material for a secondary battery represented by the following chemical formula 2 containing Mn as essential.
Li _a Ni _1-x-y-z Co _x (Mn _{s Alt} ) _{y M'z} O _2-w A _w (2)
In the above formula,
M'is at least one selected from the group consisting of Ti and Mg.
A is an oxygen-substituted halogen and
1.00 ≦ a ≦ 1.5, 0 <x <y, 0.2 ≦ x + y ≦ 0.4, 0 <s ≦ 1, 0 ≦ t <1, and 0 ≦ w ≦ 0.001. z is determined by the doping element according to the content defined in claim 1.

On the other hand, according to another embodiment of the present invention, a positive electrode containing the positive electrode active material is provided.

Further, a secondary battery having a structure in which an electrode assembly including the positive electrode, the negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode is impregnated in the electrolytic solution is built in the battery case. Provided.

Hereinafter, the present invention will be described in more detail.

According to one embodiment of the invention, it comprises a lithium nickel-based oxide doped with a doping element (M').
The doping element (M') is one or more selected from the group consisting of titanium (Ti) and magnesium (Mg).
When the doping element (M') is Ti, the doping content is 3000 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element.
When the doping element (M') is Mg, the doping content is 500 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element.
When the doping element (M') is Ti and Mg, the positive electrode active material for a secondary battery has a total doping content of 3500 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element. To.

That is, the doping content of the doping element (M') for exerting the effect of the present invention is determined by what kind of doping element is doped.

In other words, it depends on whether the doping element is titanium (Ti) alone, magnesium (Mg) alone, or whether titanium (Ti) and magnesium (Mg) are doped together.

Specifically, when the doping element (M') is Ti, the doping content may be 3000 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element, and more specifically, 3000 ppm. It may be up to 4000 ppm.

When the doping element (M') is Mg, the doping content may be 500 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element, and more specifically, 1000 ppm to 5000 ppm. It may be present, and more specifically, it may be 2000 ppm to 4000 ppm.

Alternatively, when the doping element (M') is Ti and Mg, the total doping content may be 3500 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element, and more specifically, 4000 ppm. It may be up to 5000 ppm.

If the doping content is out of the above range and the doping content is too small, the effect of preventing particle cracking of the positive electrode active material cannot be obtained as an effect of the present invention. It is not desirable because the element can easily cause the cracking of particles due to the decrease in the stability of the crystal structure of the lithium nickel-based oxide.

On the other hand, as a result of repeated in-depth studies by the inventors of the present application, it has been found that the doping element (M') is most preferable in the case of Ti, and it is preferable that it contains at least Ti.

Specifically, in the past, various elements were disclosed as doping elements, but if excessively large amounts of doping elements are required, the manufacturing cost will increase and the original high nickel content of lithium nickel-based oxidation will occur. It is not desirable as it affects the properties exhibited by the object. That is, the doping amount that prevents the particles from cracking but does not affect the characteristics of the lithium nickel-based oxide itself is most preferably in the above range. Nevertheless, some doping elements have a problem that a large amount of doping is required in order to exert the effect of preventing particle cracking, whereas when the above range is satisfied, the most excellent particle cracking occurs. The element that exhibits the preventive effect is Ti.

However, although there is a limit to the improvement of particle cracking compared to Ti, in the case of Mg, the effect of improving particle cracking is shown even with a smaller doping amount, so when trying to exert the effect with a smaller amount, Mg is used. It is preferable to use.

For this reason, when Ti and Mg are all contained as the doping element (M'), the content ratio thereof may be 1: 9 to 9: 1 with respect to the weight, and more specifically, Ti. Is the most preferable effect for improving particle cracking, and may be 5: 5 to 9: 1.

On the other hand, the lithium nickel-based oxide according to the present invention is specifically represented by the following chemical formula 1.
Li _a Ni _{1-x-y-z Co x My} M'z O _2-w A _w (1)
In the above formula,
M is at least one selected from the group consisting of Mn and Al.
M'is at least one selected from the group consisting of Ti and Mg.
A is an oxygen-substituted halogen and
1.00 ≦ a ≦ 1.5, 0 <x <y, 0.2 ≦ x + y ≦ 0.4, and 0 ≦ w ≦ 0.001, and z is defined in claim 1 by a doping element. It is determined according to the content of the product.

Specifically, the lithium nickel-based oxide according to the present invention may be a lithium transition metal oxide containing Ni and Co as essential and at least one element of Mn and Al as essential.

Further, such a lithium transition metal oxide may be doped with Ti and / or Mg.

More specifically, the lithium nickel-based oxide is represented by the following chemical formula 2 containing Ni, Co, and Mn as essential.
Li _a Ni _1-x-y-z Co _x (Mn _{s Alt} ) _{y M'z} O _2-w A _w (2)
In the above formula,
M'is at least one selected from the group consisting of Ti and Mg.
A is an oxygen-substituted halogen and
1.00 ≦ a ≦ 1.5, 0 <x <y, 0.2 ≦ x + y ≦ 0.4, 0 <s ≦ 1, 0 ≦ t <1, and 0 ≦ w ≦ 0.001. z is determined by the doping element according to the content defined in claim 1.

When such an active material is used, it is most excellent in the effect of improving particle cracking by doping the element limited by the present invention.

The doped lithium nickel-based oxide is not limited to the conventional method of adding a doping element to the lithium transition metal oxide to be doped, and can be produced by any method, for example, Ni-. A Co-M precursor can be produced, and thereafter, a lithium precursor and a doping (M') precursor can be mixed and heat-treated to produce, or a lithium nickel-based oxide containing no doping element can be produced. The doping precursor can be subsequently mixed and heat-treated to produce, more specifically, a Ni-Co-M precursor is produced, and thereafter, a lithium precursor and a doping (M') precursor are mixed and heat-treated to produce the Ni-Co-M precursor. can do.

On the other hand, according to still another embodiment of the present invention, a positive electrode containing the positive electrode active material is provided, and also includes the positive electrode, a negative electrode, and a separation film interposed between the positive electrode and the negative electrode. A secondary battery having a structure built in a battery case with the electrode assembly impregnated with the electrolytic solution is provided.

Specifically, the secondary battery may be a lithium secondary battery.

In addition to the lithium nickel oxide, the positive electrode active material includes LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₂ , and Li _{(Nia Cob Mn c )} O ₂ (0 <a <0.8, 0 < _b <. 1, 0 <c <1, a + b + c = 1), LiNi _{1-d Cod} O ₂ , LiCo _1-d Mn _d O ₂ , LiNi _1-d Mn _d O ₂ (0.2 <d <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _2-e Ni _e O ₄ , LiMn _2-e Co _e O ₄ (0 <e <2), LiCoPO ₄ , LiFePO ₄ , etc. may be mentioned, and of course, a mixture of any one or more of these may be further contained in a small amount.

However, the lithium nickel-based oxide is contained in an amount of at least 60% by weight or more based on the weight of the total positive electrode active material.

The positive electrode is formed by applying a positive electrode material further containing a conductive material, a binder, and if necessary, a filler, and the like, in addition to the positive electrode active material, onto the positive electrode current collector.

The conductive material is used to impart conductivity to an electrode, and can be used without any special limitation as long as it has electron conductivity without causing a chemical change in the constituent battery. .. Specific examples include carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; graphite such as natural graphite and artificial graphite; copper, nickel, and aluminum. Metal powders or metal fibers such as silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like alone. Alternatively, a mixture of two or more can be used. The conductive material is contained in an amount of 1% by weight to 30% by weight, specifically 1% by weight to 10% by weight, and more specifically 1% by weight to 5% by weight, based on the total weight of the positive electrode material.

The binder plays a role of improving the adhesion between the positive electrode active material particles and the adhesive force between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacryllonerile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and the like. Examples include regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-dienepolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof. , One of these alone or a mixture of two or more can be used. The binder is contained in an amount of 1% by weight to 30% by weight, specifically 1% by weight to 10% by weight, and more specifically 1% by weight to 5% by weight, based on the total weight of the positive electrode material.

The positive current collector is not particularly limited as long as it has conductivity without inducing a chemical change in the battery, and is, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel. Surface-treated surfaces such as carbon, nickel, titanium, and silver can be used. Further, the positive electrode current collector can have a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesive force of the positive electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a non-woven fabric.

The negative electrode can also be manufactured in a form in which a negative electrode material containing a negative electrode active material is applied onto a negative electrode current collector, and the negative electrode material is also a conductive material and a binder as described above together with the negative electrode active material. , Additional fillers may be included as needed.

As the negative electrode active material, a compound capable of reversible insertion and desorption of lithium can be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn. Metallic compounds that can be alloyed with lithium, such as alloys or Al alloys; metal oxides that can be doped and dedoped with lithium, such as SiO _x (0 <x <2), SnO ₂ , vanadium oxide, lithium vanadium oxide. ; Or a complex containing the metallic compound and a carbonaceous material such as a Si—C complex or a Sn—C complex, and any one or a mixture of two or more of these can be used. Further, a metallic lithium thin film may be used as the negative electrode active material. As the carbon material, low crystalline carbon, high crystalline carbon and the like can all be used. Typical examples of low crystalline carbon are soft carbon and hard carbon, and examples of high crystalline carbon include amorphous, plate-like, scaly, spherical or fibrous natural graphite or Artificial graphite, Kish graphite, thermally decomposed carbon (pyrolic carbon), liquid crystal pitch carbon fiber (mesophase platinum based carbon fiber), carbon microspheres (meso-carbon microbeads), liquid crystal pitch (meso-carbon microbeads), liquid crystal pitch High-temperature calcined carbon such as petroleum or coal tar pitch divided cokes is typical.

The negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery, and is, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and the like. The surface of copper or stainless steel can be surface-treated with carbon, nickel, titanium, silver, etc., or an aluminum-cadmium alloy can be used. Further, the negative electrode current collector can usually have a thickness of 3 μm to 500 μm, and similarly to the positive electrode current collector, fine irregularities are formed on the surface of the current collector to bond the negative electrode active material. You can also strengthen your power. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a non-woven fabric.

The separation membrane separates the negative electrode and the positive electrode and provides a passage for moving lithium ions, and can be used without any special limitation as long as it is usually used as a separator in a lithium secondary battery, and in particular, it can be used. Those having low resistance to ion transfer of the electrolyte and excellent in the moisture-containing capacity of the electrolytic solution are preferable. Specifically, polyolefin-based high polymers such as porous polymer films such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers and ethylene / methacrylate copolymers. A porous polymer film made of molecules or a laminated structure having two or more layers thereof can be used. Further, a normal porous non-woven fabric, for example, a non-woven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, or the like may be used. A coated separation membrane containing a ceramic component or a polymer substance may be used for heat resistance or mechanical strength assurance, or may be selectively used in a single layer or a multilayer structure.

The electrolyte used in the present invention includes an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte that can be used in the production of a lithium secondary battery. Examples include, but are not limited to, electrolytes.

Specifically, the electrolytic solution can contain an organic solvent and a lithium salt.

The organic solvent can be used without any special limitation as long as the ions involved in the electrochemical reaction of the battery serve as a movable medium. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; dibutyl ether. Ether-based solvents such as (dibutyl ether) or tetrahydrofuran (tellahydrofuran); ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; dimethyl carbonate, dimethylcarbon. ), Dithylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylenecarbonate (ethylene carbonone, EC), propylene carbonate (propylenePC), etc. Alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; R-CN (R is a linear, branched or ring-structured hydrocarbon group of C2-C20 and contains a double-bonded aromatic ring or ether bond. Nitriles such as (may be); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or solvents and the like can be used. Among them, a carbonate-based solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate) having a high ionic conductivity and a high dielectric constant that can enhance the charge / discharge performance of the battery and a low-viscosity linear carbonate-based compound (for example). For example, a mixture with ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) is more preferable. In this case, the performance of the electrolytic solution can be improved by mixing the cyclic carbonate and the chain carbonate in a volume ratio of about 1: 1 to about 1: 9.

The lithium salt can be used without any special limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salts are LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (C ₂ F ₅ SO). ₃ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiCl, LiI, or LiB (C ₂ O ₄ ) ₂ can be used. The concentration of the lithium salt is preferably used in the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so that excellent electrolyte performance can be exhibited and lithium ions can be effectively transferred.

In addition to the above-mentioned components, the electrolytic solution contains a haloalkylene carbonate such as difluoroethylene carbonate for the purpose of improving the life characteristics of the battery, suppressing the decrease in the battery capacity, improving the discharge capacity of the battery, and the like. System compounds, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N, N-substituted imidazolidine, One or more additives such as ethylene glycol dialkyl ether, ammonium salt, pyrrol, 2-methoxyethanol or aluminum trichloride may be further contained. At this time, the additive is contained in an amount of 0.1% by weight to 5% by weight based on the total weight of the electrolytic solution.

As described above, the secondary battery according to the present invention can be used as a device power source in a portable device such as a mobile phone, a laptop computer, a digital camera, and a device power source in the electric vehicle field such as a hybrid electric vehicle (HEV). Is.

Hereinafter, examples of the present invention will be described in detail so that a person having ordinary knowledge in the technical field to which the present invention belongs can easily carry out the present invention. However, the present invention is feasible in a variety of different forms and is not limited to the examples described herein.

<Comparative Example 1>
NiSO _{4.6H 2} O as a nickel precursor, CoSO _{4.7H 2 O as a cobalt precursor, and MnSO 4.7H 2 O as} a manganese precursor are used, and Ni: Co: Mn is mixed at a molar ratio of 65:15:20. A metal salt aqueous solution was produced from distilled water so as to be charged, and charged into a supply tank of a co-precipitation reactor (capacity 20 L, rotary motor output 200 W).

After putting 3 liters of distilled water into the coprecipitation reactor, dissolved oxygen was removed while supplying nitrogen gas at a rate of 2 liters / minute, and the mixture was stirred at 140 rpm while maintaining the temperature of the reactor at 50 ° C. ..

Further, 14 M concentration of NH ₄ (OH) as a chelating agent was continuously added to the reactor at 0.06 liter / hour, and 8 M concentration of NaOH solution as a pH adjuster was continuously added to the reactor at 0.1 liter / hour. The input amount was appropriately controlled so as to maintain the pH in the reactor at 12 during the course of the process.

After that, the coprecipitation reaction was carried out by adjusting the impeller speed of the reactor to 140 rpm while pouring the metal salt solution from the metal salt aqueous solution supply tank at 0.4 liter / hour.

After that, the obtained precipitate was filtered, washed with water, and dried in an oven at 100 ° C. for 24 hours to obtain hydrate precursor particles of Ni _0.65 Co _0.15 Mn _0.20 (OH) ₂ . Manufactured.

After that, the lithium precursor (LiOH) is set to 1: 1 with respect to the hydrate precursor particles, and TiO ₂ is added so that Ti is 1000 ppm with respect to the weight of the positive electrode active material excluding the doping element. After dry mixing, this is placed in a furnace and fired at 850 ° C. for 10 hours to be Ti-doped LiNi _0.648 Co _0.15 Mn _0.20 Ti _0.002 O ₂ positive electrode active material. Manufactured.

<Example 1>
In Comparative Example 1, as a doping precursor, TiO ₂ was dry-mixed so that Ti was 3000 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.644 Co _0.15 Mn _0.20 Ti. Except for the fact that _0.006 O ₂ was produced, the positive electrode active material was produced in the same manner as in Comparative Example 1.

<Example 2>
In Example 1, as a doping precursor, TiO ₂ was dry-mixed so that Ti was 5000 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.64 Co _0.15 Mn _0.20 Ti. Except for the fact that _0.01 O ₂ was produced, the positive electrode active material was produced in the same manner as in Example 1.

<Example 3>
In Example 1, as a doping precursor, MgO was dry-mixed so that Mg was 1000 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.646 Co _0.15 Mn _0.20 Mg ₀ . Except for the production of _.004 O ₂ , the positive electrode active material was produced in the same manner as in Example 1.

<Example 4>
In Example 1, as a doping precursor, MgO was dry-mixed so that Mg was 2000 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.642 Co _0.15 Mn _0.20 Mg ₀ . Except for the production of _.008 O ₂ , the positive electrode active material was produced in the same manner as in Example 1.

<Example 5>
In Example 1, as a doping precursor, MgO was dry-mixed so that Mg was 4000 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.634 Co _0.15 Mn _0.20 Mg ₀ . A positive electrode active material was produced in the same manner as in Example 1 except that _1.016 O ₂ was produced.

<Comparative Example 2>
In Example 1, as a doping precursor, TiO ₂ and MgO are dry-mixed so that Ti is 1000 ppm and Mg is 2000 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.64 Co ₀ . _.15 A positive electrode active material was produced in the same manner as in Example 1 except that Mn _0.20 Ti _0.002 Mg _0.008 O ₂ was produced.

<Example 6>
In Example 1, as a doping precursor, TiO ₂ and MgO are dry-mixed so that Ti is 2500 ppm and Mg is 1000 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.641 Co ₀ . _.15 A positive electrode active material was produced in the same manner as in Example 1 except that Mn _0.20 Ti _0.005 Mg _0.004 O ₂ was produced.

<Example 7>
In Example 1, as a doping precursor, TiO ₂ and MgO are dry-mixed so that Ti is 3500 ppm and Mg is 1500 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.637 Co ₀ . _.15 A positive electrode active material was produced in the same manner as in Example 1 except that Mn _0.20 Ti _0.007 Mg _0.006 O ₂ was produced.

<Example 8>
Instead of the manganese precursor, Al ₂ (SO ₄ ) ₃ · H ₂ O was used as the aluminum precursor, and Ni: Co: Al was mixed at a molar ratio of 65:15:20 to make Ni _0.65 Co _0.15 . Positive electrode of LiNi _0.646 Co _0.15 Al _0.2 Ti _0.004 O ₂ in the same manner as in Example 1 except that hydrate precursor particles of Al _0.20 (OH) ₂ were produced. Manufactured active material.

<Comparative Example 3>
In Example 1, as a doping precursor, TiO ₂ was dry-mixed so that Ti was 450 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.6491 Co _0.15 Mn _0.20 Ti. Except for the production of _0.0009 O ₂ , the positive electrode active material was produced in the same manner as in Example 1.

<Comparative Example 4>
In Example 1, as a doping precursor, TiO ₂ was dry-mixed so that Ti was 5500 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.639 Co _0.15 Mn _0.20 Ti. Except for the fact that _0.011 O ₂ was produced, the positive electrode active material was produced in the same manner as in Example 1.

<Comparative Example 5>
In Example 1, as a doping precursor, MgO was dry-mixed so that Mg was 450 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.648 Co _0.15 Mn _0.20 Mg ₀ . A positive electrode active material was produced in the same manner as in Example 1 except that _.002 O ₂ was produced.

<Comparative Example 6>
In Example 1, as a doping precursor, MgO was dry-mixed so that Mg would be 5500 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.628 Co _0.15 Mn _0.20 Mg ₀ . A positive electrode active material was produced in the same manner as in Example 1 except that _.022 O ₂ was produced.

<Comparative Example 7>
In Example ₁ , ZrO2 was dry-mixed as a doping precursor so that Zr was 2000 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.648 Co _0.15 Mn _0.20 Zr. Except for the fact that _0.002 O ₂ was produced, the positive electrode active material was produced in the same manner as in Example 1.

<Comparative Example 8>
In Example 1, as a doping precursor, ZrO2 was dry _- mixed so that Zr was 4000 ppm with respect to the weight of the positive electrode active material excluding the doping element, and LiNi _0.646 Co _0.15 Mn _0.20 Zr. Except for the fact that _0.004 O ₂ was produced, the positive electrode active material was produced in the same manner as in Example 1.

<Experimental Example 1>
The positive electrode active materials of Examples 1 to 8 and Comparative Examples 1 to 6 were placed in a sample holder and rolled to 9 tons using Carver's rolling density measuring device to obtain the specific surface area (BET) before rolling and the specific surface area (BET) after rolling. The specific surface area (BET) was measured and the results are shown in Table 1 below.

The "specific surface area" is measured by the BET method, and is specifically calculated from the amount of nitrogen gas adsorbed under liquid nitrogen temperature (77K) using BELSORP-mino II manufactured by BEL Japan. did.

With reference to Table 1 above, it can be confirmed that when the positive electrode active material according to the example was rolled in the same manner, the particles were less cracked than the positive electrode active material of the comparative example.

<Experimental Example 2>
The positive electrode active materials produced in Examples 1 to 8 and Comparative Examples 1 to 6 were used, PVdF was used as a binder, and natural graphite was used as a conductive material. The positive electrode active material: binder: conductive material was well mixed with NMP so as to have a weight ratio of 96: 2: 2, then applied to an Al foil having a thickness of 20 μm, and then dried at 130 ° C. to produce a positive electrode. A lithium foil was used as the negative electrode, and a half-coin cell was manufactured using an electrolytic solution containing 1 M LiPF6 in a solvent of EC: DMC: DEC = 1: 2: 1.

The half-coin cell is fully charged at 0.33C to 4.3V, the cell is disassembled, the positive electrode and the separation membrane are washed with a Dimethyl Carbonate (DMC) solution, and then the positive electrode and the separation membrane dried in the air are placed in an Al pouch. After newly injecting the same electrolytic solution as above, the pouch was vacuum-sealed to produce a pouch for measuring the amount of gas generated. While storing the manufactured pouch at a high temperature of 60 ° C for 4 weeks, using Archimedes' principle, the pouch was placed in a water tank containing a certain volume of distilled water and the mass in water was measured. The volume change of the pouch was calculated using the density according to the temperature of water at the time of measurement. The results of the measured gas generation amount are shown in Table 2 below.

With reference to Table 2, it can be confirmed in Table 1 that the smaller the cracking of the particles and the smaller the BET change rate, the better the high temperature storage performance.

<Experimental example 3>
The half coin cell manufactured in Experimental Example 2 is charged at 45 ° C. under constant current / constant voltage (CC / CV) conditions at 1C to 4.3V, and then charged at constant current (CC) conditions at 1C up to 3.0V. It was discharged, and the discharge capacity was defined as one cycle discharge capacity. This was repeated up to 400 cycles, and the value calculated by (capacity after 400 cycles / capacity after 1 cycle) × 100 was defined as the high temperature life retention rate (%), and the results are shown in Table 3.

With reference to Table 3, it can be confirmed in Table 1 that the smaller the number of particles cracked and the smaller the BET change rate, the better the high temperature life characteristics.

The positive electrode active material according to the present invention is accompanied by an increase in the specific surface area of the positive electrode active material by minimizing the cracking of particles even in high pressure rolling by doping optimization containing a specific doping element at a specific content. It has the effect of solving the increase in resistance during high-temperature storage due to the generation of gas due to the increase in side reactions with the electrolytic solution, and improving the life characteristics.

Claims (10)

Contains lithium nickel oxides doped with a doping element (M')
The doping element (M') is one or more selected from the group consisting of titanium (Ti) and magnesium (Mg).
When the doping element (M') is Ti, the doping content is 3000 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element.
When the doping element (M') is Mg, the doping content is 500 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element.
When the doping element (M') is Ti and Mg, the total doping content is 3500 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element, which is a positive electrode active material for a secondary battery. The secondary battery according to claim 1, wherein when the doping element (M') is Ti, the doping content of Ti is 3000 ppm to 4000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element. Positive active material. The secondary battery according to claim 1, wherein when the doping element (M') is Mg, the doping content of Mg is 2000 ppm to 4000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element. Positive active material. The secondary battery according to claim 1, wherein when the doping element (M') is Ti and Mg, the total doping content is 4000 ppm to 5000 ppm based on the total amount of the lithium nickel-based oxide excluding the doping element. Positive active material for. The positive electrode active material for a secondary battery according to claim 1 or 4, wherein the doping content ratio of Ti and Mg is 1: 9 to 9: 1 with respect to the weight. The positive electrode active material for a secondary battery according to claim 5, wherein the doping content ratio of Ti and Mg is 5: 5 to 9: 1 with respect to the weight. The lithium nickel-based oxide is represented by the following chemical formula 1 and is represented by the following chemical formula 1.
Li _a Ni _{1-x-y-z Co x My} M'z O _2-w A _w (Chemical formula 1)
In the chemical formula 1,
M is at least one selected from the group consisting of Mn and Al.
M'is at least one selected from the group consisting of Ti and Mg.
A is an oxygen-substituted halogen and
1.00 ≦ a ≦ 1.5, 0 <x <y, 0.2 ≦ x + y ≦ 0.4, and 0 ≦ w ≦ 0.001, and z is defined in claim 1 by a doping element. The positive electrode active material for a secondary battery according to any one of claims 1 to 6, which is determined according to the content thereof. The lithium nickel-based oxide is represented by the following chemical formula 2 and is represented by the following chemical formula 2.
Li _a Ni _1-x-y-z Co _x (Mn _{s Alt} ) _{y M'z} O _2-w A _w (Chemical formula 2)
In the chemical formula 2,
M'is at least one selected from the group consisting of Ti and Mg.
A is an oxygen-substituted halogen and
1.00 ≦ a ≦ 1.5, 0 <x <y, 0.2 ≦ x + y ≦ 0.4, 0 <s ≦ 1, 0 ≦ t <1, and 0 ≦ w ≦ 0.001. The positive electrode active material for a secondary battery according to claim 7, wherein z is determined by a doping element according to the content defined in claim 1. A positive electrode containing the positive electrode active material for a secondary battery according to any one of claims 1 to 8. 2. The structure is such that the electrode assembly including the positive electrode, the negative electrode, and the separation film interposed between the positive electrode and the negative electrode according to claim 9 is impregnated in the electrolytic solution and is built in the battery case. Next battery.